A conjunction is used to connect words and sentences

OFFICIAL EXPLANATION






• OVERVIEW

Part of this question hinges on logic.
Option E might give you the clue if you do not catch the simple logic at first: we do not connect words TO sentences.
From that incorrect option, you might infer that we also do not connect words AND sentences.

Why on earth would we use a conjunction to connect words (noun, adjective, e.g.) AND sentences (subject/verb/object, e.g.)?
No, no, no.
Sentences are collections of words.

Using the conjunction and, we connect [different] words.

→ My favorite fruits are pomegranates and cherries.

→ Aaron and Aanya are twins.

Using the conjunction and, we connect [different] sentences.

→ We are such stuff as dreams are made on, and our one little life is rounded with a sleep. (Shakespeare, The Tempest)

→ One day I will find the right words, and they all will be simple. (Jack Kerouac, The Dharma Bums)

• THE OPTIONS - elimination


• Logical error
We do not use "and" to connect words and sentences.
We use "and" to connect grammatical items of equal weight: words and words, phrases and phrases, clauses and clauses, and so on.

• Redundancy
The word connect means "to bring together."
Together is implied in the verb connect and is thus redundant, irrespective of logic.
ELIMINATE A


• Redundancy
→ The same problem as that in option A: the verb "connect" implies "together."
HOLD. Look for a better answer.
(On the first pass, I rarely eliminate options on the basis of redundancy.)


• Illogical
→ By definition, the coordinating conjunction and connects items of equal grammatical weight.
A word and a sentence are not "items of equal weight."

→ As is the case in option A, the meaning is illogical.
We do not connect words and sentences (or words TO sentences, for that matter).
We connect words to other words.
We connect sentences to other sentences.
ELIMINATE C


• Correct. Now we can toss out option B.
(At the least, option D is better than B because option D eliminates the unnecessary word together.)

• This sentence is logical (words-words, sentences-sentences) and stylistically superior to B ("together" is both redundant and wordy).
KEEP


• Illogical
We do not use conjunctions to connect words and sentences; nor do we use conjunctions to connect words TO sentences.

This option might have given you an "aha" moment.
That is, if we think about the matter, we do not use conjunctions to connect words to sentences.

Why not?
Well, sentences are composed of words, for one thing.
It sounds weird to say that we want to connect words TO sentences.

At that point, we might notice the and/or split and realize that the word and is, logically, very close to this incorrect word, to.
Then we could eliminate options A, C, and E. Between B and D? We don't need "together."
Done.

The answer is D.

This question is a bit sneaky.
It is also instructive. Don't miss the forest for the trees. (Google that idiom if you do not know what it means.)
Sometimes we get too focused on small rules and we cannot "take the satellite view" or see the big picture.

It is good to be reminded now and then that we must be on the lookout for opportunities to use simple reasoning.

COMMENTS

bobnil , welcome to SC Butler.

These answers are good.
In fact, bobnil , I am bumping you to Best Community Reply.
zhanbo , you and bobnil tied, but I have already bumped you a couple of times—so .
. . . we will welcome the newcomer.

To any other non-expert newcomers or lurkers who would like to join, you are always invited to do so.

Good work.